A Brief History of Sidings

Perhaps because they represent a mysterious unseen underworld, disused Underground stations seem to fascinate a lot of people – including those who aren’t generally interested in trains. You could be forgiven for thinking that Underground sidings would carry the same cachet, but they seem to be a subject that is often overlooked.

The majority of London’s underground sidings today have a curious property – almost none of them seem to be used for the purpose for which they were originally intended. We have seen the exceptional case of Smithfield sidings primarily used for freight, but most subterranean sidings were primarily constructed to enable trains to terminate well short of the end of an underground line in order to reduce the number of lightly-loaded trains running all the way to the terminus station. A siding was a relatively cheap option compared with the alternative of a very expensive extra platform – especially on the deep-level tubes.

Deep-level sidings were regularly used on London Underground until the latter part of the 20th century. If you travelled on the underground in the 1960’s you would find destinations such as Liverpool Street, Marble Arch, Archway or Tooting Broadway quite commonplace. Even in the early 1970’s the newly-finished Victoria line regularly had timetabled trains terminating at both Victoria and King’s Cross.

Today, with a more intensive service, the operational philosophy has changed. There are often enough passengers to justify a service from one end of the line to the other which has the benefit of offering a “turn-up and go” service. More critically, with today’s frequent service it is often just not possible to terminate a train in the central area or inner suburbs and check that there are no passengers still on board without delaying the train behind. This is even more true now that it is mandatory to check that no passengers remain on the train. Indeed when the Victoria line was extended to Brixton it was quickly realised that by the time the train was emptied at Victoria, had gone into the sidings, the driver walked down through the eight car train and he had returned northbound in his allocated slot he might just as well have gone to Brixton in revenue-earning service. If you ever wonder why quiet semi-rural places like Cockfosters have such a good service it is simply because there are very few places suitable to terminate trains previously without causing disruption.

The consequence of all this is that expensive underground sidings could not be justified on the basis of their original purpose. Given that they are quite costly to maintain does that mean that they are practically redundant? Not a bit of it!

Any Port in A Storm

The first justification for a siding today is as a “cripple siding”. Basically if a train cannot move at normal speed under its own power, the controller will be desperate to get it off the running lines as soon as possible so that the service can continue. In effect, this is the railway operational equivalent of “any port in a storm”.

This might not be a frequent use of a siding but when used it can mean the difference between “good service” and “service suspended”. On its own this is almost sufficient justification for a siding such as Down Street on the Piccadilly line to be maintained, despite it being extremely inconvenient in many ways – not least the fact that the only permitted way to exit is to walk along the main tracks to Hyde Park Corner. Similarly another siding which is of limited use, but which is still retained, is that at the former British Museum station on the Central line.

Use as a cripple siding is not just limited to passenger trains. If there is a problem with an engineering train at night, or simply the fact that it cannot return to base without impacting on the first trains in service, then the sensible thing is to get it off the “main line” using the nearest available stabling point and worry about it after the end of the day’s service.

Start the Day As You Mean To Go On

The second use of sidings is to be able to provide a decent service from the first train of the day right up to the last train of the day. Obviously this is more important if part of the line is distant from the main depot or depots. For this reason the underground terminus stations of Walthamstow Central, Brixton and Elephant and Castle have sidings beyond the platforms, as did Charing Cross (Jubilee line) when it was open and they are presumably still available for use now. In the case of Elephant & Castle the nearest depot is actually extremely close, but it is awkward to get from there to Elephant & Castle station as it involves a reversal on the running tracks.

Sidings at such locations may seem unnecessary, as the trains could potentially stable in the platforms. This is certainly possible but the sidings also conveniently double as an overrun, allowing the trains to approach the platform at speed as there is no need for “train protection at terminal stations” (colloquially known as “Moorgate control”). Having a train in a siding also means that if it fails at the start of the day, it doesn’t block a platform. It also means that maintenance can be carried out on the track within the platform area itself at night. Generally once a week, however, (usually on a Friday or Saturday night) the train is stabled in the platform. This obviously allows regular inspections and maintenance carried out on the siding itself.

Recovering the Service

The third main benefit of a siding is that it is somewhere to get rid of a train when the service falls to pieces. If a controller experiences a problem on the line (such as a ten minute delay because a door won’t close) then one of the biggest problem this creates is that it causes the trains to bunch. This potentially leaves a number of trains stuck in tunnels for long periods of time. The best and quickest way to get rid of this problem is to thin out the service until it is running smoothly again, and then to reintroduce the trains removed from service in a gradual and orderly manner.

One problem in this situation is that it is almost always worst where the stations are closest – the central section. This is, of course, precisely the section where sidings and other places to temporarily store trains are scarcest. Here the Central line is very fortunate as it has 16 sidings located underneath the Westfield shopping centre at White City which used to be 15 open-air sidings before the over-development. The Victoria line is probably the line that suffers the most, with it possessing no non-intensively used section and being entirely underground. South of Seven Sisters it also only has intermediate sidings at Victoria (2) and King’s Cross (1). Also, as London Underground delight in telling us, the line currently has 37 trains but only 33 platforms, so evacuating people in the event of a train failure becomes quite problematic – and that is before they introduce even more trains at the final stage of the upgrade.

Terminating Early

Another use of sidings is to terminate a train short of destination in order to regulate the service (fill a gap going the other way) but nowadays this can easily become problematic. The driver has a limit to the hours he is allowed to drive and he may be sent away from his signing-on point. Furthermore, the train must return to its home depot at least every 48 hours for a mandatory check and messing around with train diagrams may cause this to be missed. It is a situation not helped by the fact that a controller will not instantly know where the train and the driver are based, which nowadays need not be the same place. Slightly different (but certainly related) is the train held in a siding specifically for the finish of a big event but with the current frequencies run this becomes less of either an option or a necessity.

Doubling Up

At some places other than termini there are actually two sidings. Liverpool Street (Central line) and Victoria (Victoria line) both have two. Victoria actually used to have four but two were used to extend the line to Brixton. More unusually, Down Street (between Green Park and Hyde Park Corner on the Piccadilly line) and Kennington have a double-length siding. In the case of Kennington there is even a second exit half way down, so that one train is not trapped behind another. Due to a fatal accident at Tooting Broadway, however, where it was suspected that the driver mistook his location for the longer siding at Kennington, it has since been the policy to only provide signalling for one-berth at these locations.

This is no great loss. A second berth at Down Street isn’t really needed and Kennington also has a loop although this can only be accessed from the Charing Cross branch. One way around this for the future though would be to arrange for the trains to enter into the sidings unmanned. This would also overcome the problem of leaving the driver trapped with his train for long periods, as well as making it easier for trains to enter and exit sidings by a shunt manoeuvre so that sidings could be used “from the wrong direction”. Of course the problem of the trapped driver would have been less of an issue in true “tube” sidings if a pedestrian exit had been provided, but this is almost never the case. It is said, however, that the siding at Kennington has an exit to Oval station and this does seem plausible given how long it is and how close the end of it is to that station.

The Northbound Trailing Junction at Kennington. The loop is to the right. By Owen D.Smithers.

It is probably a sign of how useful sidings continue to be that there is only one case of a deep-level siding not still being in use. That is at Queensway, but it is located east of the station and must be approached from the west which limits it value. It is also close to the siding at Marble Arch and the far better facilities at White City which are only four stops further down the line. It may be the case that the siding simply was not long enough for the current length of trains which brings us to the issue of sidings being too short.

Length Matters

One of the often forgotten problems of extending train length is that the sidings (and depots) may not be able to accommodate the longer trains. Although it may not be too difficult to extend sidings underground, it would normally be expensive and involve legal procedures before work could start. There is a case of a surface siding at Golders Green that needed extending from six to seven cars but the hillside was in the way. The siding was extended by creating a third tunnel mouth (the Northern line surfaces at Golders Green) that only extends into the hillside by one carriage length.

Luckily, it appears that short sidings have so far not been a problem for the deep level tubes. The situation is, however, quite different for the sub-surface lines – especially with the introduction of the longer S7 stock. After all, there is no equivalent of simply introducing selective door operation if the siding is too short.

With the main depots on the sub-surface lines being a long way out (Hammersmith, Neasden, Upminster) it is important to have stabling sidings located nearer the centre. The situation is made worse because the current ones (Farringdon, Parsons Green and “Triangle Sidings” near Gloucester Road) cannot be extended easily. In particular Triangle Sidings, more conveniently located than Parsons Green, is a very tight fit even for C6 stock and, due to it both being built over and also abutting the running lines, it is almost impossible to extend. So the hunt is on for alternative options and as mentioned in our article about the Widened lines it seems that the likely solution is to convert these to a long linear siding with the advantage of trains being able to depart in either direction. It is fortunate that these lines have been returned to London Underground, the owners, as a result of the Thameslink Programme. These would of course for the most part be located underground.

It must not be forgotten that there are also subterranean sidings on the National Rail network. Smithfield carriage sidings are located to the west of the running lines between City Thameslink and Farringdon, with the buffer stops almost by Farringdon station. As such the name is slightly misleading and also easily confused with the former Smithfield goods sidings. Unfortunately the two sidings cannot be extended from the current eight carriages and so will be only useable by a proportion of the proposed Thameslink stock. The overhead wires have been extended southwards from Farringdon to City Thameslink and the eventual intention is that in the northbound direction the changeover from AC to DC would takes place at City Thameslink. In the event of a pantograph or similar failure the train could simply continue to Smithfield sidings where it would stable until a convenient opportunity was available to send it to the depot at Three Bridges for the fault to be rectified.

It must not be forgotten that the Waterloo & City line manages in this as in many other cases to be completely different and uniquely has a complete underground depot where the trains are serviced. One suspects that space is extremely cramped. Whilst it is unlikely that the train length will ever be extended due to the difficulty of extending the platforms at Bank it is not known if an extra train could be accommodated if required. Currently there are five trains based there and all five are in service in the morning peak. At present there are no extra trains available, but when the stock is replaced it will presumably be desirable to have a spare – provided there is somewhere to put it.

Looking to the Future

It would seem then that underground sidings are important to running a reliable service on a deep-level underground line, even though the intention may not be for them to be used on a regular basis. It comes as a bit of a surprise therefore that Crossrail appear to have to have absolutely nowhere (sidings or otherwise) planned as a potential emergency stabling point anywhere between Old Oak Common and Stratford/Abbey Wood. The proposed sidings at Westbourne Park for Paddington terminators may be built, but this is by no means certain. There is also probably land available to build or improve a surface siding at Plumstead, but this is almost at the end of the line anyway. There will be a crossover in the central area, which may help in some circumstances but not others. One presumes that the decision not to have any underground sidings on Crossrail was made on the basis that they are very expensive and should not be necessary on a modern reliable railway. It may well be the right decision, but if not it will be almost impossible to correct…

Sad story. The third platform at Liverpool Street (Circle etc. lines) was decommissioned in times of austerity and less traffic than nowadays. When they wanted to reinstate it it counted as a new works. Unfortunately it was non-compliant with current regulations and with the loss of grandfather rights it was impossible to reinstate it as it currently is. A real shame because if there are problems at Aldgate or similar one would want to try to get people as far as Liverpool Street. I suspect that the extra length of S7 over C6 means that no realistic practical modifications exist that would get it reinstated.

“This is even more true now that it is mandatory to check that no passengers remain on the train.”

That may well be true for trains terminating early in central London, but I can personally vouch that Bakerloo trains terminating at Queen’s Park are “emptied” via a simple flashing of the lights and a couple of announcements on the tannoy. I imagine it’s a holdover from the old way of running things, though, and probably not part of off

“This is even more true now that it is mandatory to check that no passengers remain on the train.”

That may well be true for trains terminating early in central London, but I can personally vouch that Bakerloo trains terminating at Queen’s Park are “emptied” via a simple flashing of the lights and a couple of announcements on the tannoy. I imagine it’s a holdover from the old way of running things, though, and probably not part of official policy, but that seems to be how they do it. I don’t imagine that would be acceptable on the shinier new trains in the busy central London stations, though.

@Bricked
It seems to be a new practice to flash the lights at Queen’s Park; they used to always have someone spend an inordinate amount of time slowly checking each carriage and closing the doors, one by one. Perhaps it’s to speed up dwell time at the station or something?

If you really wanted to, you could probably re-arrange the sidings at Moorgate so that the current inner rail line was a siding, and the terminators became part of the running lines ….
Expensive, but just do-able (I think) with a platform re-arrange/re-consrtuct as well!

I was a guard on the Northern line in the early 1980’s in the days of the 1959 stock. I was in Kennington sidings many times, and there is no access to Oval station from there. It is or certainly was infested with rats. There is also the sidings north of Archway, and if my memory is OK, i remember sidings at Tooting Broadway. A couple of times we we sent into the link tunnel to the Picadilly line between Euston and Kings Cross. To keep the trains going which had door sticking problems, there was a carriage examiner at Euston who came aboard with an oil can, to lubricate the rollers.

The disused bay platform at Liverpool Street is now being used for a new substation. I think that it is part of the sub-surface lines power upgrade, although work appears to be arranged in coordination with the Crossrail works (presumably to minimize station closures).

Thanks Former Guard for your comments. I had my doubts about the link to Oval and was looking for confirmation or denial. I also wondered when I wrote the article whether the link tunnels were usable and if so if they got used for stabling – now I know. One thing I didn’t cover in the article is that I get the impression that tube sidings are pretty unpleasant places. Well, staff stuck there with a desperate need to do certain things and possibly an inviting pile of sand nearby by the buffer stops for starters. Also the lack of ventilation. Didn’t think about the rats though.

City of London is the owner of most of the railway lands around Farringdon/Smithfield, not LUL. JB touched on this in his Walk on the Widened Lines, and the potentially significant disagreement over whether the siding tunnels should revert back to CoL if they are not in “operational use”. Apparently there are lots of examples where Network Rail have a long-term lease rather than the freehold on railway lands, and the terms of the original lease may become significant if the land is no longer used by the railway. The same is likely to be true for LUL. CoL may be seeking to cash in on some useful real estate, or simply trying to reduce the cost of maintenance. But given the lengths it was prepared to go to with Smithfield Market, this may be not be a trivial passing spat.

The Smithfield Sidings just north of Thameslink could have been extended, but this would have had to been integrated into the design of the new Crossrail station. Perhaps there was not the length, or perhaps they just didn’t think of it. As we’ll see in an upcoming piece, the railway lands around Farringdon were extensive, and the old Great Northern goods depot would have allowed additional platforms at Farringdon as well as sidings.

If sidings are regarded of sufficiently strategic value, then the alignments should be safeguarded. Then, when sites are redeveloped, the space can be created (or recreated) beneath.

@Greg, at Moorgate, even if they couldn’t reconstruct the inner ring platform as an island with a central reversing siding, couldn’t they remove the Thameslink platforms and put sidings in there?

Kennington sidings:
As previously mentioned, there is no exit to Oval station from the sidings. There is an exit to the running tunnel in the form of a cross passage (except that it goes down steps as the siding is higher than the running tunnel) at the far end of the siding (I have photos somewhere).

There is no second exit halfway down. Franklin’s Carto-Metro map shows the siding to scale. The first part of the track from the SB main is in fact the siding approach (SB movements only). On a steep uphill slope, this was protected by spring catch points, recently(ish) replaced with power operated points. The siding can only be exited onto the NB main via the crossover that appears to be halfway down the track. The siding starts from this point.

At one time, the siding used to be fully signalled to hold two trains, with shunt signals halfway down – one to allow movement to the end of the siding, the other to allow movement from the end of the siding to the siding exit shunt signal. These were later replaced by a fixed transtop. A train going to the end of the siding had to trip past this. Although the end of the siding was very rarely used in later years, it was useful for stabling two trains that had been coupled together (e.g. a defective train and assisting train).

These days, since the (longer) buffer replacement, two trains will not easily fit due to the reduced siding length and it is no longer taught that the siding can hold two trains. However, it is still possible to just fit two 95 stock trains (or two coupled) in if required although it is a very tight squeeze and the exit shunt signal cannot be seen from the cab

As regards the conditions, generally Kennington siding wasn’t bad, especially after the installation of staff toilets off the SB platforms. The exit from Kennington loop is another matter though!

Euston / Kings Cross loops:
These are also normally used for reversing trains, but not stabling.
The Kings Cross loop joins the Northern and Piccadilly lines and is used for movements between the two lines, especially engineers trains. It is also a convenient reversing point for trains reversing South – North. Trains go from Euston (City) via the Euston loop and then stop in the Kings Cross loop and reverse. It is a way of getting late running Kennington CX trains back on time, the train just sits there until about four minutes before its Camden Town time.

In theory the Euston loop could be used to stable a train, but the only time I can see that happening is if the train is defective in rush hours and they just want to leave the train there until they can get it to depot (probably Golders Green) afterwards. The loop is normally used as a means of reversing NB trains N-S at Euston. Although passengers can be taken NB through the Euston loop, they are normally detrained at Kings Cross for two reasons. 1) The next NB train from Euston will be the one that departs from KX and so there is no point in passengers getting off at Euston and then walking all the way over to the NB platform. 2) The tyrain may be held for some time in the loop.

Regarding the need to fully detrain before each reversal, this was imposed by HMRI after a fatality at Liverpool Street about ten years ago when an overcarried passenger panicked and fell between cars while walking through the train. I’ve tried googling but can’t find record of the incident, but off the top of my head it was c.2000. When I was a Guard going into Kennington Loop in the late 1990’s, you’d use your Guard’s key to activate an automatic announcement and then just shut the doors and go. Likewise, when I became a driver on the District Line, reversing at Parson’s Green or Barking sidings, you’d just make three PAs and go (often meeting some overcarried passengers in the sidings). It was while I was a driver that it changed, so before 2001.

However, as has been alluded to, this is now changing. The key is ‘Inner inter-car barriers’, a permanent barrier either side of the interconnecting doors which prevent someone from falling between the cars if they were using the communicating doors. On the Bakerloo they’re just plain foam-like pads, but those currently being installed on the Jubilee are an interesting toothed design… the new procedure used on the Bakerloo will come to the Jubilee soon, as ORR are now satisfied that the risk is sufficiently mitigated via the Inner inter-car barriers.

Charring Cross sidings / platforms on the Jubilee can hold up to six trains I believe, but it can only be entered from the Southbound so has it’s limitations.

Reversing trains in a siding is most often from my experience done because of train drivers driving time limitations – not in spite of. Ie the controller wants to run the train in much in service as possible, so if a driver only has an hour left to drive – or the service is so bad that they’re running very late, they may be turned early to get back to the ‘train crew accommodation’ or depot on time. The alternative would be the driver leaving the train in the depot which means another driver having to make the 15 minute+ journey to get the train back out of the depot – and of course it would likely be that available drivers are at one end of the line and the driver booked to pick up that train now at the other.

I worked on the W&C too occasional, it was rather ‘tight’ but was improved from what it was. Apparently the layout of one of the roads meant stabling too near to the wall at the end, which contravenes some safety law or other (understandable) so several million was spent changing it around.

Regarding the new inner inter-car barriers making it OK to take customers into sidings, it’ll still be interesting to see whether drivers are willing to do it, as the concern is that without checking beforehand you could be stuck alone in a siding and at risk of assault should there be a customer on board the train.

Many thanks for all the comments, extra information and clarifications from those “in the know”.

Jubilee Driver, you are of course absolutely correct in that controllers will use sidings to turn trains around to get drivers back to the depot. After writing the article I noticed a comment concerning this on aslefshrugged’s website and had intended to modify my article in light of it but didn’t get around to it.

The point I was trying to make was that a controller is nowadays more reluctant to turn a train around in order to fill a gap in the other direction because of hours restrictions etc. What I failed to state is that the corollary is that a controller may well turn a train around because of a driver’s restrictions regardless of the gap in the service it may create. Obviously with the more frequent service we have today long gaps in service should be less of an issue.

In the seventies, the off-peak and weekend pattern of service from Morden was generally Morden – Mill Hill via Bank, Morden – Colindale via Bank. The Colindale reversers were annoying because there were no toilet facilities there – you came off at Golders Green or just used the sidings, whilst keeping an eye out for passing trains. There also wasn’t a tea point (boiling water supply) at Colindale. Therefore the usual procedure was for the driver to get off and fill his tea can at Golders Green and the tea would be nicely brewed by the time you got to Colindale!

At peak hours, the sidings at Tooting Broadway were in continuous use for reversing trains, with trains usually blocking back on the south because the train in the platform was waiting for the trian in the siding to depart so it could then go in there. There was often blocking back on the north if the train was late departing the siding. There wasn’t usually that much turn round time and if the train was late arriving in the siding for whatever reason, it was often due out again within a few minutes. If the NB trains were running on time, the signal from the siding might be cleared on time, even though the driver might not be in position yet. The next NB train would then be held after departing Colliers Wood. It wasn’t unknown for trains to be blocking back as far as South Wimbledon as a consequence. Depending on the amount of delays caused by subsequent reversers, the blocking back could be extended. At times, trains were waiting outside Morden to get into the platforms because of the delay on the NB.
Archway had the occasional timetabled peak reverser.

This changed in later years as more passengers were using the Northern line and the trains were extended to Edgware / Morden. At around the same time, they also got rid of the dreaded Kennington – Golders Green (middle platform) via Charing Cross reversers. These were mind numbingly boring!
From then on, the sidings were normally only used for short-tripping trains except for the two later timetables where they introduced Archway – Tooting reversers off peak.

Kennington siding has been used at times for timetabled reversing, usually for Bank branch trains and only at peak times, although there was at least one timetable I remember where Bank trains were booked to reverse at Kennington off peak. I also seem to remember one timetable where some CX trains were booked to reverse there off peak insteak of going round the loop, possibly so that the trains ended up going north from platform 1in a different sequence to when they arrived at platform 2. The problem with using Kennington sidings was the delay that was often caused. As can be seen from the layout, a CX train going into the siding from platform 2 will hold up southbound trains from platform 4, so any delays detraining meant that trains to Morden were also delayed if the shunt signal for the siding was already off. Departing from the siding, whether to platform 1 or 3 often used to delay NB trains from Morden.

From an operational point of view, not having timetabled reversing at sidings was one less headache. Fewer delays were caused to the service due to the train being delayed whilst detraining or while in the siding (in the siding, it was common practice for the crew to meet in the middle of the train when changing ends and then natter or swap tea. Often the signal would have been cleared for many minutes before the driver got into their cab).

There is also the real risk of a SPAD at the signal protecting the exit from the siding. This is particularly so at B34 (Kennington) and NN14/15A at Archway where the signals are approach-controlled and don’t clear when expected. This, of course, is another source of delay which, depending on the circumstances, could end up a major one.

I was a signalman on the Central Line many moons ago. Remember having to go to Holborn on Sunday’s to do the “rusty rail move”, signalling an empty train into the sidings and back out to test the emergency reversing point was in working order!

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